Optically induced metal-to-dielectric transition in Epsilon-Near-Zero metamaterials.
Optically induced metal-to-dielectric transition in Epsilon-Near-Zero metamaterials.
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DOI：
10.1038/srep27700
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发表时间：
2016-06-13
影响因子：
4.6
通讯作者：
Faccio D
中科院分区：
文献类型：
--
作者：
Kaipurath RM;Pietrzyk M;Caspani L;Roger T;Clerici M;Rizza C;Ciattoni A;Di Falco A;Faccio D
ε-近零材料在介电常数的真实的部分中表现出作为波长的函数从正值到负值的转变。在这里，我们研究金属-电介质层状超材料的均匀制度（每一层具有强烈的亚波长厚度）与零真实的部分的介电常数在近红外区域。通过光学泵浦的超材料，我们实验表明，接近ε近零（ENZ）波长的介电常数表现出显着的过渡，从金属（负介电常数）电介质（正介电常数）作为光功率的函数。值得注意的是，这种转变作为泵浦功率的函数是线性的，并且发生在100 fs泵浦脉冲的量级的时间尺度上，其不需要被调谐到特定波长。介电常数增加的线性度允许我们根据标准三阶光学非线性来表达超材料的响应：这示出了真实的部分和虚部在穿过ENZ波长时的作用的明确反转，进一步支持超材料的物理行为中的光学诱导变化。
Epsilon-Near-Zero materials exhibit a transition in the real part of the dielectric permittivity from positive to negative value as a function of wavelength. Here we study metal-dielectric layered metamaterials in the homogenised regime (each layer has strongly subwavelength thickness) with zero real part of the permittivity in the near-infrared region. By optically pumping the metamaterial we experimentally show that close to the Epsilon-Near-Zero (ENZ) wavelength the permittivity exhibits a marked transition from metallic (negative permittivity) to dielectric (positive permittivity) as a function of the optical power. Remarkably, this transition is linear as a function of pump power and occurs on time scales of the order of the 100 fs pump pulse that need not be tuned to a specific wavelength. The linearity of the permittivity increase allows us to express the response of the metamaterial in terms of a standard third order optical nonlinearity: this shows a clear inversion of the roles of the real and imaginary parts in crossing the ENZ wavelength, further supporting an optically induced change in the physical behaviour of the metamaterial.